Remote control apparatus



A g. 25, 1936.- iq. EAGN W 2 52,336 REMOTE CONTROL APPARATUS Filed Au 30, 1934 1 Y- Y1 Y2 Control Office i Field Stations I INVENTOR Norman EAgnew.

H16 ATTORNEY Patented Aug. 25, 1936 PATENT OFFICE 2,052,336 REMOTE CONTROL APPARATUS Norman F. Agnew, Swissvalc, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application August 30, 1934, Serial No. 742,088

6 Claims.

My invention relates to remote control apparatus, and particularly to apparatus for use in connection with a remote control system in which a line circuit is employed for signalling between a control ofiice and remote stations.

The principal object of my invention resides in the provision of means for overcoming the detrimental effects of imperfect insulation betweenthe two conductors of the line circuit in a system of this character, whereby the distortion of the line signals due to leakage currents is minimized, the operation of the system under unfavorable weather conditions is improved, and the extent of territory and number of stations that can be controlled over a single line circuit is increased.

I will describe two forms of apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 illustrates diagrammatically a typical line circuit for a remote control system including one form of apparatus of my invention. Fig. 2 illustrates another form of the apparatus of my invention in which the use of a local battery is avoided.

Similar reference characters refer to'similar parts in each of the views.

Referring to Fig. 1, the references Y, Y! and Y2 designate the different sections of the line control wire comprising one side of the line circuit of a typical remote control system, while conductor Z is the common return conductor which may be either a return wire or the earth. The line circuit formed by conductors Y and Z includes a line battery LB, located at the control oflice shown at the left in the drawing, a current limiting resistor 6, a line relay OR at the oflice and line relays such as RI, R2, R3, etc., including one at each of the several stations. The system also includes a transmitter relay OT at the office, provided with a contact I in the line circuit, which contact may be opened and closed repeatedly to signal from the ofiice to the stations. Each field station has a similar transmitter relay, such as relay T3 at the most remote station which,

as shown, is provided with a contact 2, which may be opened and closed repeatedly to signal from the transmitting station to the office. To illustrate the efiect of imperfect insulation be- 50' tween the line conductors, I have shown a resistance X representing a leakage path from conductor Y2 to conductor Z on the oflice side of the most remote station, but it is to be understood that, in general, the line leakage is likely 'to be more or less uniformly distributed and may be represented by a large number of very high resistances connected in multiple across the line conductors. In any case, however, it will be clear that when there is an appreciable flow of current through the leakage path or paths the control of relay OR at the office by contact 2 of relay T3 may be interfered with. Thus in Fig. 1, when contact 2 opens, if no corrective measures are applied to the system the current through relay OR will decrease gradually due to the discharge of the stored inductive energy of relays OR, RI, and R2 through the shunt path which includes resistance X, at a rate which depends upon the resistance of this shunt path so that relay OR will act as a slowrelease relay. Furthermore, when contact 2 is closed, relay OR will become more highly energized if a leakage current is superimposed upon the normal line current and will tend to release more slowly when the contact opens for this reason as well. Unless the leakage is so great as to render the system inoperative by holding relay OR steadily energized, its principal efiect, therefore is to distort the signals repeated by line relay OR at the battery end of the line circuit.

As an illustration of the magnitude of these effects under actual conditions, it has been found that in one system of remote control in which the normal line current is 100 milliamperes and the line relays are adjusted to pick up on 50 milliamperes and to release on 30 milliamperes, if contact 2 is operated repeatedly to produce equal on and off periods of current in the line, at the usual signaling speed, the front and back contacts of relay OR will be closed for equal periods of time as long as the line is well insulated, but when the value of the leakage current is such as to cause milliamperes to flow through relay OR when contact 2 is open, the release of relay 0R will be retarded so that its front contact will be closed twice as long as its back contact during each cycle of operation, while if the leakage current is 27 milliamperes, the periods when contact 2 is open will be bridged and the front contact of relay OR will be closed continuously.

In order to overcome these detrimental effects I provide a leakage unit comprising a pair of relays RP and RL which are inserted in series in the line circuit at the oilice. Relay RP is a line relay similar to the line relays OR, R3, etc., of the remote control system, while relay BL is a double wound stick relay having a line winding 3 and a front contact 4 included in the line circuit and an auxiliary winding 5. To pick up relay RL I provide a circuit which may be traced from one terminal B of a local source of energy over back contact I of relay RP, winding 5 of relay RL to the other terminal C of the same source of energy, so that relay RL will pick up to close contact 4 to establish the line circuit whenever relay RP is deenergized. Relay RL differs from the other line relays in that its line winding 3 has less turns, so that relay RL will release upon a value of 60 current in winding 3 which is at least equal to and preferably is greater than the value at which the other line relays pick up. In practice, I prefer to adjust relay RL so that it'will release when the current in winding 3 is reduced to about milliamperes when the other line relays are adjusted to pick up on 50 milliamperes. With this adjustment, winding 3 of relay RL, willbe but feebly energized when contact 2 is closed, even though the maximum permissible leakage current is superimposed upon the normal line current, and in consequence of its feeble energization and high release point, relay RL will release quickly when contact 2 opens, for any value of leakage current less than the value which will cause relay OR to remain steadily energized. It is clear, therefore, that the distortion of the line circuit may be greatly decreased by including relay RL in the circuit and by. this means the system may be made operative without detrimental distortion for any value of leakage current up to the value whichwill cause the line relay OR to be held steadily energized.

The operation of the system of Fig. 1, when transmitting from a remote station to the control office, is as follows:

When transmitter contact 2 of relay T3 at the.

remote station opens, relay RL at the ofiice, because of its marginal adjustment, releases quickly even though the current through the leakage path at X is almost suflicient to maintain relay OR energized. The opening of contact 4 of relay RL opens the line circuit so that relays OR and RP release quickly. As soon as. relay RP releases, the pickup circuit for relay RL becomes closed and relay RL again picks up and closes contact 4 in the line circuit. Since, as assumed, the leakage current is insufficient to pick up relays OR and RP, these relays will remain in the release position, as long as transmitter contact 2 remains open. When contact 2 closes, relays OR and RP pick up, and relay RP opens contact 1 so that:

relay BL is again rendered responsive to the line current in winding 3.

It is obvious that, if desired, relay RP may be omitted and winding 5 of relay RL may be controlled by a back contact of relay OR, since relays OR and RP are alike. The arrangement illustrated in Fig. 1 is however considered preferable because it can be applied to an existing system without any change in the apparatus of the system.

Fig. 2 shows an alternative arrangement in which I control the leakage unit without the use of a local battery. In Fig. 2, contact I of relay RP is arranged as a continuity transfer contact, and the portion of the line circuit which includes the leakage unit may be traced from wire YO,

through relay RP and winding 3 of relay RL,

front contact 1 of relay RP, front contact 40f relay RL to line wire Y. When relay RL releases, contact 4 opens and relay RP becomes deenergized and releases. The pickup circuit for relay RL may then be traced from wire YO, through relay RP, winding 3 of relay RL, back contact 1 of relay RP,rwinding 5 of relay RL to line wire Y. Both windings 3 and 5 are now connected in series so that relay RL will pick up on a comparatively low value of line current to close contact 4, which contact, however, is not included in the line circuit as long as relay RP is deenergized. It is evident that winding 5 of relay RL, in Fig. 2, becomes deenergized when relay RP picks up, and that the apparatus of Fig. 2 functions in substantially the same manner as that of Fig. 1.

Although I have herein shown and described only two forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a normally energized line circuit including a line relay adapted to release upon a relatively large reduction in current,

'a stick relay having a line winding and a front contact in said line circuit, said stickrrelay being adapted to release upon a relatively small reduction in current in said line circuit, and means including an auxiliary winding on said stick relay effective to pick up said stick relay contact when the line relay releases.

2. In combination with a normally energized.

line circuit including a line relay adapted to release upon a relatively large reduction in current, a stick relay having a line windingand a front contact in said line circuit, said stick relay being adapted to release upon a relatively small reduction in current in said line circuit, and means including a back contact of. the line relay and an auxiliary winding of said stick relay for picking up the stick relay to close said contact.

3. In combination, a line relay, a stick relay having two windings, a normally closed line circuit including a source of current, one winding and a front contact of said stick relay and said line relay, and a pickup circuit for said stick relay including its other winding and a back contact of said line relay.

4. In combination, a line relay, a stick relay, a pickup circuit for the stick relay including a back contact of the line relay, a winding of the stick relay and a source of current, and an energizing circuit for the line relay including a winding'and a front contact of the stick relay and a source of current.

5. In combination, a line relay which picks up on a predetermined value of current and releases on a lower value of current, a stick relay having a line winding effective to hold it picked up only when the current through said winding is at least equal to that required to pick up the line relay, a

normally closed line circuit including a source of current, said line winding and a front contact of said stick relay and said line relay, and a pickup circuit for said stick relay including another winding of the stick relay and a back contact of the line relay.

6. In combination, ',a line circuit including a source of current and a normally closed contact, a line relay in said circuit which picks up on a predetermined value of current and which releases on a lower value of current, means included in said line'circuit for opening said contact in' response to a reduction in the current in' said line circuit when said current is greater than said predetermined'value, and means for closing said contact irrespective of the value of the cur-' rent in said line circuit when said line relay becomes released.

NORMAN F. AGNEW. 

